This invention relates to an air conditioning system including a damper blade assembly rotatably mounted within a duct provided to deliver conditioned air to an enclosure, and in particular, to an arrangement for controlling the position of the damper blade assembly within the duct in accordance with the sensed supply air pressure and temperature of the air in the enclosure.
Many multiroom structures, such as office buildings and schools, constructed during the past several years, include air conditioning systems to deliver either relatively warm or cool conditioned air from a central source thereof to each of the enclosures or rooms in the building. Typically, one or more ducts are employed to deliver the air to each enclosure. Very often, a damper blade assembly or similar mechanism is installed in the duct to regulate the flow of air to one or more diffusers or discharge outlets located in the enclosure being conditioned by the discharge of air thereinto. The movement of the damper blade assembly may be responsive to changes in the conditioned air supply pressure and/or changes in the temperature of the enclosure.
In some air conditioning systems of the prior art, as represented by U.S. Pat. Nos. 3,143,292 and 3,554,112, the diffusers or discharge outlets located in the enclosure being conditioned have included an inflatable bellows to regulate the flow of conditioned air into the enclosure. Inflation of the bellows has been controlled through a device responsive to the pressure of the supply air to maintain a substantially constant volume flow of conditioned air into the enclosure. In addition, in some of the systems, a temperature responsive device has been combined with the pressure responsive device to reduce the flow of conditioned air as the temperature in the enclosure approaches a desired predetermined level. The pressure responsive device delivers a pressure signal to the bellows which is proportional to but less than supply air pressure. As the temperature of the air in the enclosure approaches a predetermined set point, the temperature responsive device will function to increase the magnitude of the signal to the bellows to increase the inflation thereof. When it is desired to eliminate all flow of conditioned air, the pressure signal to the bellows will essentially approach the supply air pressure.
In other air conditioning systems, it has been found desirable to regulate the flow of air through the duct by providing a damper blade assembly within the duct upstream of the discharge outlets or diffusers. A bellows is inflated in direct response to changes in the supply air pressure to maintain a substantially constant volume flow of conditioned air. Typically, unlike the arrangements disclosed in the above-cited patents, the bellows pressure is approximately identical to the supply air pressure. Thus, if it is desired to decrease the air flow as the temperature in an enclosure approaches a predetermined level or set point, an additional force must be generated to move the damper blade assembly.
U.S. Pat. Nos. 3,806,027 and 3,945,565 illustrate various arrangements heretofore available to regulate the flow of conditioned air through a duct by modulating the position of a damper blade assembly mounted within the duct. However, none of the prior art patents heretofore cited illustrate the arrangement of the present invention which has been found to be extremely effective in regulating the flow of air through a duct to a plurality of discharge outlets whereby the flow of air is maintained substantially constant irrespective of any changes in the conditioned air supply pressure. The present invention includes temperature responsive means to reduce the flow of air below the predetermined level as the temperature in an enclosure approaches a predetermined set point.